This invention relates generally to a portable position detector and a position management system, and more particularly to a portable position detector capable of estimating the moved position of a walking body (e.g., a person) by self-contained navigation (number of stepsxc3x97length of a step) and a position management system capable of managing the positions of a plurality of portable position detectors.
A variety of vehicle navigational systems have been developed. At the beginning, self-contained navigation was used to provide information about the location of a vehicle. Later, self-contained navigation and a global positioning system (GPS) were combined into a hybrid system. The self-contained navigation employs an integration system. That is, the outputs from a speed sensor are integrated to detect the traveled distance of a vehicle, and the direction of the vehicle is detected from a direction sensor such as a gyro. The direction detected for each predetermined distance or time and the distance traveled during that period are cumulatively added to the starting point to detect the current position.
On the other hand, portable position detectors utilizing the GPS have recently been developed in order to render the measurement of the position of a walker possible. However, in the GPS, the position of a walker cannot be calculated unless information is received from 4 satellites (or 3 satellites although measurement accuracy is reduced). Since walkers walk on mountains and valleys and, even in a city, walk on a sidewalk that is easily shaded by buildings, the portable position detector is considerably disadvantageous in the above-mentioned reception, compared with vehicle navigational systems that are employed in vehicles traveling on a roadway in the central portion between buildings. In addition, a speed sensor cannot be simply applied to a walker, as in vehicle navigational systems.
Hence, the ideas of self-contained navigation for walkers, which employ a pedometer, have hitherto been proposed in Japanese Laid-Open Patent Publication Nos. HEI 2-216011, HEI 5-172579, HEI 8-68643, and HEI 9-89584.
However, the above-mentioned conventional methods have the following disadvantages when measuring the position of a walker. That is, the direction of a walker can always be detected at any point, while a pedometer can detect only whether or not a single step of a walk has been made. For example, the pedometer cannot continuously detect the moved distance of the center of gravity of a walker""s body, which is continuously moved during a single step of a walk. Therefore, unlike vehicle navigational systems, at what point a moved distance and a moved direction are detected and used as a base of the calculation of the position of a walker is considerably important for the position detection of a walker based on self-contained navigation, because particularly when a walk involves a curve, the direction of the body easily changes even during movement of a single step of a walk.
In the above-mentioned 4 publications, Japanese Laid-Open Patent Publication No. HEI 9-89584 has no description of how a moved distance and a moved direction are determined.
On the other hand, the aforementioned Japanese Laid-Open Patent Publication No. HEI 8-68643 discloses that when a cantilever vibration meter (pedometer) with a weight outputs a pulse signal, the direction at that time is employed to calculate a moved distance. However, in this vibration meter (pedometer), a pulse signal is generated by the vertical movement of the center of gravity of a walker when the vibration meter strikes the weight that attempts to keep its position by inertia. Note that all pedometers are uniformly set so that a pulse signal is generated when the aforementioned gravity of center rises by a predetermined distance (about 15 mm). Also, since there is a great shock when a walker lands on a surface such as a road, the output of the vibration meter gives rise to hunting. For this reason, this vibration meter is constructed so that an electric circuit cuts the hunting (i.e., a signal at the time of landing is not used). Therefore, if a moved direction is detected at the time of the generation of this output pulse, the moved direction will often be detected when a walker begins to change a direction. As a result, it cannot be expected to select an optimal moved direction, and a measured position is often departed from the moved position.
Japanese Laid-Open Patent Publication Nos. HEI 2-216011 and HEI 5-172579 disclose that the direction of a walker is constantly detected and that it is judged whether or not the direction has been changed. If it is judged that the direction has been changed, the direction and distance up to this point are stored in order. As occasion demands, a position and a walked route are calculated from the stored data. This method judges a change in a moved direction by whether or not a measured direction has exceeded a reference range of direction that becomes a predetermined change of direction. However, when a measured direction exceeds the reference range of direction, there is no description of which direction of the moved directions being changed up to that time within the reference range of direction is employed in the measurement of a moved position.
In the aforementioned case, if the range of a reference value is narrow, the direction of a walker will constantly change and become complicated. At the same time, the information will be too much for the storage capacity, so the reference value must be set wide to some degree. If the reference value is set wide, the dispersion will become increasingly great, depending on the direction used before change of direction. Particularly, in a long and gentle curve or an inclined road, an error will be cumulated.
Also, in many cases, pedometers are constructed so that they count the number of steps and cumulate a value obtained by multiplying the number of steps by the length of a step, thereby displaying a walked distance. However, in practice, the step length of a walker is not constant. For this reason, this method has the disadvantage that the calculation accuracy of a walked distance is insufficient. For example, it is general that the length of a step varies between when the walker is hurried and when the walker walks slowly. However, in the conventional method, since a walked distance is calculated without giving consideration to variations in the length of a step due to a difference in a walking state, the accuracy of the walked distance is insufficient.
It is an object of the present invention to provide a portable position detector and a position management system that are capable of enhancing the accuracy of the position of a walking body detected by self-contained navigation, by accurately detecting the direction of the walking body even when GPS signals cannot be received or even when no GPS signals are received and also changing the length of a step in accordance with the walking state.
To achieve this end and in accordance with a first preferred form of the present invention, there is provided a portable position detector for detecting a moved position of a walking body. The portable position detector comprises: (1) walking-motion detection means for measuring a value related to a walking motion caused by movement of the walking body; (2) acceleration detection means for detecting acceleration of the value related to the walking motion caused by movement of the walking body; (3) moved-distance estimation means for estimating the moved distance of the walking body, based on both a number of steps detected from an output of the walking-motion detection means and a step length changed according to horizontal acceleration of the walking body or the magnitude of a change in the horizontal acceleration detected by acceleration detection means; (4) moved-direction detection means for detecting a direction or direction of movement of the walking body caused by movement of the walking body; (5) moved-direction determination means for detecting two points at which the walking body arrives substantially at a highest position and lands by walking, based on the walking motion caused by movement of the walking body that is output by the walking-motion detection means, and also for determining a moved direction at a specific point as a specific moved direction, the specific point being related to at least one of the detected two points and also being specified in a range between the highest-position arrival point and the highest position at which the waling body arrives substantially by the next walking; and (6) moved-position estimation means for estimating a position of the walking body after movement, based on the moved distance of the walking body estimated by the moved-distance estimation means and the specific moved direction determined by the moved-direction determination means.
Thus, the walking-motion detection means can easily grasp the highest-position arrival point and/or landed point of a walker by the output pattern of the geomagnetic sensor or the acceleration sensor. For the moved direction of the walker, the direction of the walker at a point in a range, in which the walker lands from the high-position arrival point and then raises the next foot to the highest position, is closer to the moved direction than the direction of the walker at a point at which the walker begins to raise the foot thereof. Therefore, if one of the aforementioned two points is grasped, then an optimal specific point in the aforementioned range can be selected at the one point or a point delayed from the one point by a predetermined time (i.e., a point related to the aforementioned point). As a result, a more superior moved direction can be selected.
The change of a step length is generally performed in consideration of the fact that in the case of a hurried walk the step length is large, in the case of a normal walk the step length is shorter than the hurried walk, and in the case of a slow walk the step length is shorter than the normal walk, and furthermore in consideration of the fact that these step lengths are considerably stable if viewed individually, although they depend mainly on height (foot length), the strength of a kick, and age. The above-mentioned three kinds of walks are sufficient for the step length. Although it cannot be said that there is no possibility that the length of a step will change continuously between the three kinds, the step length cannot continue to change continuously for a long time. Conversely speaking, a walker changes the time required for one step, depending on the degree of hurry. If this change becomes greater, the walker will change the step length to a step length peculiar to the person that is not fatigued. This changed step length is continuously repeated for a relatively long time in about three kinds mentioned above. Therefore, these step lengths may previously be measured individually and registered. Or during a walk, the walking time, the number of steps, and the walked distance obtained with a global positioning system (GPS) may be measured and registered.
As one method, the present invention determines a step length changed according to the horizontal acceleration of a walking body or the magnitude of a change in the acceleration. In this case, the vertical acceleration of a waling body and a change in this acceleration are also related to the horizontal acceleration and a change in the horizontal acceleration.
In another method, the time required for one step is detected, and according to the length of the detected time, the length of a step is changed in consideration of the busyness of the foot motion. In the former employing only acceleration, there is a need to view the gain and complicated motion of the acceleration and the cost is increased. On the other hand, the latter case has the advantage that measurements can easily be made.
The aforementioned moved-distance estimation means performs the process of estimating the moved distance of a walking body with the number of steps detected from the output of the walking-motion detection means, as a parameter. The number of steps in this case means that one step of a walk has been performed, and this is most desirable. However, the present invention is not limited to one step of a walk. Even in the case of an increased number of steps, the estimation of the moved distance of a walking body is possible. Normally, walking rhythm will be substantially constant, so the length of a step may be changed when it continuously changes considerably as a whole.
In accordance with the aforementioned first preferred form of the present invention, even in the case where the position detector is located in a forest or between buildings where a signal cannot be received from a global positioning system (GPS) due to high buildings, banks, and forests, the position detector with a portable size and weight applicable to a walker can know the position of a person carrying this portable detector by self-contained navigation. In this case, when the moved direction of a walker required for measurement is determined, easy detection becomes possible by grasping the highest-position arrival point or landed point of a body, such a foot or a waist, with a geomagnetic sensor or an acceleration sensor. If the moved direction at a point, which is in a range between a point related to the aforementioned point (i.e., the aforementioned point or a point delayed from the aforementioned point by a predetermined time) and the highest position that a walker arrives at by the next walking motion, is used as a specific moved direction for measurement, the moved direction of a walker can be determined at a point at which the direction of the body of a walker becomes closer to the moved direction. With this, measurement accuracy can easily be enhanced.
Also, by detecting changing environment, the length of a step can be changed according to a slopping road, etc. As a result, position accuracy can be further enhanced. In addition, the position detector according to the present invention can be produced at low cost.
Furthermore, the accuracy of a step length can be enhanced considerably by correcting the step length in accordance with the acceleration (i.e., the horizontal acceleration of a walker or a change in the horizontal acceleration) of a value related to motion caused by movement of the walker (walking body). Also, the calculation accuracy of the moved distance can be enhanced. Moreover, for example, if acceleration during walking is employed as a parameter, there is an advantage that the correction of a step length can easily be judged.
In a second preferred form of the present invention, the portable position detector comprises: (1) walking-motion detection means for measuring a value related to a walking motion caused by movement of the walking body; (2) acceleration detection means for detecting acceleration of the value related to the walking motion caused by movement of the walking body; (3) moved-distance estimation means for estimating the moved distance of the walking body, based on both a number of steps detected from an output of the walking-motion detection means and a step length changed in a direction where the step length becomes a wider step length as the time required for one step of a walk detected from an output of the walking-motion detection means becomes shorter; (4) moved-direction detection means for detecting a direction or direction of movement of the walking body caused by movement of the walking body; (5) moved-direction determination means for detecting two points at which the walking body arrives substantially at a highest position and lands by walking, based on the walking motion caused by movement of the walking body that is output by the walking-motion detection means, and also for determining a moved direction at a specific point as a specific moved direction, the specific point being related to at least one of the detected two points and also being specified in a range between the highest-position arrival point and the highest position at which the waling body arrives substantially by the next walking; and (6) moved-position estimation means for estimating a position of the walking body after movement, based on the moved distance of the walking body estimated by the moved-distance estimation means and the specific moved direction determined by the moved-direction determination means.
In accordance with the aforementioned second preferred form of the present invention, the length of a step is corrected according to the time required for one step of a walk. Therefore, in addition to the advantages of the aforementioned first preferred form of the present invention, this case, as compared with the case of employing acceleration alone, is advantageous in that there is no need to view the gain and complicated motion of acceleration, the cost can be reduced, and measurements can be made more easily.
In a third preferred form of the present invention, even when the time required for one step of a walk is shorter than normal time required for one step of a walk, the step length is corrected so that the time required for one step of a walk becomes shorter, if the horizontal acceleration of the walking body or a change in the acceleration detected by the acceleration detection means during this walking is less than a first predetermined value. Also, even when the time required for one step of a walk is longer than normal time required for one step of a walk, the step length is corrected so that the time required for one step of a walk becomes longer, if the horizontal acceleration of the walking body or a change in the acceleration detected by the acceleration detection means during this walking is greater than a second predetermined value.
In accordance with the aforementioned third preferred form of the present invention, the length of a step is corrected with the time required for a single step of a walk and the horizontal acceleration at this time (or the magnitude of a change in the acceleration). With this, the correction judgement of the step length is easy, the accuracy of the step length can be enhanced considerably, and the calculation accuracy of the moved position of a walker can be enhanced. In addition, if the walking time per step and the acceleration of a walker are employed as parameters, there is an advantage that the correction judgement of the step length is easy.
In a fourth preferred form of the present invention, the moved-distance estimation means counts the number of steps on the basis of a vertical geomagnetic change caused by walking of the walking body, detected by the walking-motion detection means, and also estimates the moved distance from a relation of the counted number of steps and the length of a step. Also, the step length is corrected based on the output of the acceleration detection means when the estimation is performed.
In accordance with the aforementioned fourth preferred form of the present invention, the moved-distance estimation means counts the number of steps, based on vertical geomagnetic change caused by the walking motion of a walking body, detected by the walking-motion detection means. Also, the moved distance of the walking body is estimated by multiplying the counted number of steps and the length of a step corresponding to this number of steps. In this estimation, the step length is corrected based on the output of the acceleration detection means. Therefore, the portable and small position detector of the present invention makes self-contained navigation possible, while enhancing the accuracy of a step length.
In a fifth preferred form of the present invention, the moved-direction determination means judges and detects the highest-position arrival point and/or the landed point from a vertical acceleration change caused by walking of the walking body, and also determines a moved direction of the walking body at a specific point as a specific moved direction, the specific point being at least one of the two points, or being a point delayed from the one point by a predetermined time.
In accordance with the aforementioned fifth preferred form of the present invention, the highest-position arrival point and/or the landed point of a walking body can be detected from vertical acceleration change caused by the walking motion of the walking body. A specific point is determined as the detected point or a point delayed from one of the two points by a predetermined time. This specific point can be set to a point at which the moved direction of the walking body has become closer to the actual direction after the moved direction has changed considerably. As described above, the point is in a range between the aforementioned highest-position arrival point and the highest position that the walker arrives at by the next walking motion. As a result, measurement accuracy can be enhanced with simple detection.
In a sixth preferred form of the present invention, the moved-direction determination means judges and detects the highest-position arrival point and/or the landed point from the vertical geomagnetic change caused by walking of the walking body, and also determines a moved direction of the walking body at a specific point as a specific moved direction, the specific point being at least one of the two points, or being a point delayed from the one point by a predetermined time.
In accordance with the aforementioned sixth preferred form of the present invention, the highest-position arrival point and/or the landed point of a walking body can be detected from geomagnetic change caused by the walking motion of the walking body. A specific point is determined as the detected point or a point delayed from one of the two points by a predetermined time. This specific point can be set to a point at which the moved direction of the walking body has become closer to the actual direction after the moved direction has changed considerably. As described above, the point is in a range between the aforementioned highest-position arrival point and the highest position that the walker arrives at by the next walking motion. As a result, measurement accuracy can be enhanced with simple detection.
In a seventh preferred form of the present invention, the predetermined time that is delayed by the moved-direction determination means is determined as a proportional portion of a walking step period from a walking cycle.
In accordance with the aforementioned seventh preferred form of the present invention, the previous walking cycle is detected. Based on this walking cycle, the aforementioned delay time for determining a specific point is calculated as a proportional portion of the walking step period that becomes a specific time at which an optimal direction is obtained. Therefore, even if the state of walking changed, an optimal specific point can be kept.
In an eighth preferred form of the present invention, the predetermined time that is delayed by the moved-direction determination means is set to a time at which the specific point goes to a state in which a landed foot and the next foot are positioned side by side.
In accordance with the aforementioned eighth preferred form of the present invention, the delay time is set to or near to a time at which the specific point goes to a state in which a landed foot and the next foot are positioned side by side. Therefore, in many cases, the direction of a walker specified for calculating a measured position is closest to a moved direction. As a result, measurement accuracy can be enhanced.
In a ninth preferred form of the present invention, the moved-distance estimation means detects changing environment from acceleration change or geomagnetic change caused by movement of the walking body, also changes the length of a step, based on the detected changing environment, and calculates the estimated distance and wherein the step length is corrected based on the output of the acceleration detection means when the calculation is made.
In accordance with the aforementioned ninth preferred form of the present invention, the moved-distance estimation means is constructed so that it can detect changing environment, such as an upward slope or a downward slope, from acceleration change or geomagnetic change caused by movement of a walker. Also, when an estimated distance is calculated, the length of a step is corrected based on the output of the acceleration detection means. Therefore, the step length for calculation of a moved distance can be changed to an optimal step length in accordance with changing environment, while the accuracy of the step length is being enhanced. Thus, measurement accuracy is enhanced.
In a tenth preferred form of the present invention, the correction of the step length is performed by making the step length shorter than a step length during walk on a level path, when it is judged by the detection of the changing environment that a walking path has a slope greater than a predetermined value.
In accordance with the aforementioned tenth preferred form of the present invention, when it is judged that a walking path has a slope greater than a predetermined value, the step length is made shorter than a step length during a walk on a level path. Therefore, the aforementioned correction of the step length according to changing environment can be made more accurate than a position on a map (a position on an X-Y plane viewed from a vertical direction (Z-direction)).
In an eleventh preferred form of the present invention, the portable position detector further comprises: a unit for receiving radio waves from global positioning system (GPS) satellites and measuring the current position of the walking body; and position correction means for correcting the current position estimated by the position estimation means, when the current position is measured with the unit.
In accordance with the aforementioned eleventh preferred form of the present invention, the measuring unit employing self-contained navigation has the function of the measuring unit employing global positioning system (GPS) satellites. Therefore, where GPS signals can be received, the position based on the GPS signals is used. On the other hand, where GPS signals cannot be received, the position based on self-contained navigation is used. With this, the position of a walking body can be measured at all times. Also, the error cumulated by self-contained navigation can be cancelled by the measured position based on the GPS signals. Thus, measurement accuracy can also be assured.
In a twelfth preferred form of the present invention, when the moved direction detected by the moved-direction detection means or the specific moved direction determined by the moved-direction determination means is within a predetermined direction width and also when it is judged by the detection of the changing environment that the cumulated number of steps or the cumulated moved-distance, in which a vertical amount of movement is within a predetermined width, is a straight-advanced walk on a level path which continues for a predetermined time or more, the correction of the step length in the moved-distance estimation means is performed by a value obtained by dividing a calculated distance by the cumulated number of steps, the calculated distance being calculated from positions measured at a starting point and an ending point of the straight-advanced walk on a level path by the unit.
In accordance with the aforementioned twelfth preferred form of the present invention, only when walking is substantially a straight-advanced walk on a level path and a predetermined length or more is walked, the distance calculated with GPS signals is divided by the cumulated number of steps during the walk. In this manner, the step length is corrected. Therefore, the step length can be set to an optimal step length. Since the distance calculated with GPS signals becomes a straight-line distance, the calculation is made under a condition that walking is substantially a straight-advanced walk on a level path and a condition that walking continues over a predetermined distance or more in consideration of an error in the measurement and a change in the step length. Therefore, an enhancement in the measurement accuracy can be expected.
A position management system according to the present invention is equipped with a portable position detector for detecting a moved position of a walking body, and a base station. The portable position detector includes: (1) walking-motion detection means for measuring a value related to a walking motion caused by movement of the walking body, (2) acceleration detection means for detecting acceleration of the value related to the walking motion caused by movement of the walking body, (3) moved-distance estimation means for estimating the moved distance of the walking body, based on both a number of steps detected from an output of the walking-motion detection means and a step length changed according to either the time required for one step of a walk detected during the walking motion, or horizontal acceleration of the walking body detected by acceleration detection means, or the magnitude of a change in the horizontal acceleration, (4) moved-direction detection means for detecting a direction or direction of movement of the walking body caused by movement of the walking body, (5) moved-direction determination means for detecting two points at which the walking body arrives substantially at a highest position and lands by walking, based on the walking motion caused by movement of the walking body that is output by the walking-motion detection means, and also for determining a moved direction at a specific point as a specific moved direction, the specific point being related to at least one of the detected two points and also being specified in a range between the highest-position arrival point and the highest position at which the waling body arrives substantially by the next walking, (6) moved-position estimation means for estimating a position of the walking body after movement, based on the moved distance of the walking body estimated by the moved-distance estimation means and the specific moved direction determined by the moved-direction determination means, and (7) transmission means for transmitting at least one piece of information of output information from the walking-motion detection means, from the moved-distance estimation means, from the moved-direction determination means, and from the moved-position estimation means. The base station includes: (1) reception means for receiving the output information transmitted by the transmission means of the portable position detector and (2) display means for displaying a moved position of the portable position detector, based on the information from the reception means.
In accordance with the aforementioned position management system of the present invention, the aforementioned portable position detector (child station) is provided with transmission means in order to transmit position information to the base station (parent station). Therefore, this management system can grasp and manage the positions of respective child stations at the base station, while enhancing the accuracy of a step length at the child station side.
In the position management system, at least a portion of information necessary for a process of calculating a position of the portable position detector on the basis of a GPS signal received by the portable position detector is transmitted from the portable position detector to the base station. Also, the base station receives the portion of information and performs the position calculating process. In the portable position detector, a calculating process is shared with the portable position detector and the base station so that the base station executes processes other than the position calculating process.
In accordance with the aforementioned position management system, a portion of the information obtained by the child station is transmitted to the base station by the transmission means, and a calculating process is performed at the base station. The child station executes processes other than the calculating process. Therefore, this management system can simplify the construction of the child station, while enhancing the accuracy of a step length at the child station side. Of course, the calculation result in the base station can be transmitted to the child station so that the child station can utilize it.